public override bool Remove(TKey key)
{
if (!Splay(key))
{
return(false);
}
// Root is now the node to be removed
Debug.Assert(Root != null);
BinaryNode <TKey, TValue> leftTree = Root.LeftChild;
// 1. If the root's left subtree is empty, the root will start with the right subtree
if (leftTree == null)
{
BinaryNode <TKey, TValue> oldRoot = Root;
Root = oldRoot.RightChild;
if (Root != null)
{
Root.Parent = null;
}
oldRoot.Dispose();
Count--;
return(true);
}
// 2. Find the right-most node in the root's left subtree -- it will become the new root
BinaryNode <TKey, TValue> rightMost = null;
_traversalActions.SetActions(inAction: n =>
{
rightMost = n;
return(false); // Terminate the DFS when we find the first node
});
leftTree.SiftRight(_traversalActions);
Debug.Assert(rightMost != null); // Count > 0: there should be at least the root
// 3. Splay the right-most node
// Remove the parent of root's left child to not splay up to root
leftTree.Parent = null;
rightMost.Splay(out Root, out LastSplayDepth);
// 4. Right-most is now root of the left tree (and has no right subtree); merge it with Root
leftTree = rightMost;
Debug.Assert(leftTree.RightChild == null); // Splay on the right-most node should make it have no right (larger) children
leftTree.RightChild = Root.RightChild;
if (leftTree.RightChild != null)
{
leftTree.RightChild.Parent = leftTree;
}
Root.Clear();
Root = leftTree;
Count--;
return(true);
}